Objective        To investigate the mechanism of all-trans retinoic acid (atRA) to inhibit the adipogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs).       Methods       Rat BMSCs were isolated

incubated and induced to differentiate into adipocytes. AtRA at high concen

tration (0.1-5.0 μmol/L) was added to the medium for adipogenic induction. The morphologic changes of BMSCs during differentiation were observed under a light microscope. The effect of atRA on the adipogenic differentiation was analyzed by oil red O staining. The expression of retinoic acid receptors α and γ (RARα and RARγ)

CCAAT/enhancer binding protein a (CEBPα) and peroxisome proliferators-activated receptor γ2 (PPARγ2) was analyzed by real-time PCR.       Results        At the concentration of 0.1-5.0 μmol/L

atRA inhibited rBMSCs from differentiating into adipocytes in a dose-dependent manner. The fat content in differentiated cells was decreased along with the increase of atRA concentration (

P

0.05). Compared with the control group (without adding atRA)

the mRNA expression levels of CEBPα and PPARγ2 were decreased significantly in the atRA groups (

P

0.05). Compared with the control group

the mRNA expression of RARα in the atRA group (1.0 μmol/L) was not significantly different (0.008 4±0.001 9 vs 0.009 1±0.001 3

P

0.05)

while the mRNA expression of RARγ significantly was increased (0.022 6±0.001 2 vs 0.053 1±0.002 3

P

0.01).       Conclusion        AtRA (0.1-5.0 μmol/L) can inhibit the adipogenic differentiation of rBMSCs by up-regulating the expression of RARγ and down-regulating the expression of CEBPα and PPARγ2.